Sunday, April 17, 2011

Venco Reassembled

Yesterday I got the Venco totally reassembled and tried to pug some stoneware clay through it. The first thing I encountered was that my little taping of the screens was way too aggressive and I had to remove them and take all the tape off and then just retape the top 2.5 inches. What was happening is that clay was totally filling the slot which allows a vacuum to reach the clay. It works much better now.

But, and I accept suggestions here, it will not pull a vacuum. The vacuum pump, which is one of the old Clisbys, is working fine. If I put my finger over the hole it goes straight to 28+ inches of Hg. But with the NEW gasket in place, and just about every old and new gasket I could find or make from the stuff I have around, except the old one which I stupidly threw away, it will not go above 5 inches Hg.

Since the middle gaskets were of electrical tape, and since clay got real dry around the gaskets if the mill was not used for some time, I made new ones out of Buna-N rubber, the same rubber that separates the top and bottom pieces on my Shimpo stainless steel mill. I also made the vacuum chamber gasket out of this Buna-N rubber but it really leaks. Badly.

I have a really nice lap wheel and so took one of the metallic diamond pads and attached it to a flat piece of metal, and sanded the top of the vacuum chamber until it was flat, which took some time. Did not help a lot.

The top piece of plexiglas is the piece that came with the pugmill and it is not totally flat and many years old -- close to 25 probably. I tried some other pieces of thin plexi and they did not work either.

So. What to do? The first thing is that I will block off the vacuum chamber leading into the pugmill and make sure it's the gasket at the top of the chamber that is the problem. I think it is but it could be the Buna-N rubber which runs down the seam of the top and bottom pieces of the chamber, or the Buna-N pieces that protect the plates where the screens are extracted. I don't think it's this because the Shimpo works fine with the Buna-N.

I do not tend to have great mechanical ability. A problem like this one stumps me for some time. The mill has lots of clay in it so it's not open at the end, as a Venco can tend to be. Interesting problem.

Suggestions appreciated.

Monday, April 4, 2011

Cleaned Out Venco Pugmill

I've not cleaned out my Venco Pugmill for several years and it just seemed like the time to do it because I was not getting a good vacuum and there looked to be lots of corrosion. I had decided to install Buna N rubber gaskets all the way around to try to get the vacuum tighter, and to try to have less air seeping through the joints. When I don't use the pugmill for several months there is a noticeable dryness at the horizontal seam that runs the length of the pugmill. Venco recommends electrical tape for the joints, but over time, air gets through and it causes problems with stuff spalling off the sides into the clay, and the hardness I mentioned.

One test that I used was to take a pug and twist it, and in so doing there were air bubbles and delamination. So I decided to tape the screen aggressively so that the total amount of volume that needed to be deaired was less than before, and was nearer the vacuum chamber. As luck would have it, Rick McKinney of MKM Tools stopped by and he noticed that the screens were polished where the most clay went through and suggested that I tape with this in mind and so I did. Not sure how this will work, and for sure the mill will be slower, but I hope it helps. The mill is too fast anyway -- hard to keep up with for one person.

Monday, March 14, 2011

New Drying Molds

I mix my own clay, both stoneware and porcelain. At this point in my career I want to be sure that it is done like I want it done, and want to be able to mix small enough batches so that the formula can be flexible when conditions change. The old drying bats were just totally worn out. So we made some new ones last week. Here is a view of the process with the bus pan balanced in the wet plaster, and all the sides clamped up. We actually needed that wrench to balance the load.

A very quick little mixing formula is 2.75 pounds of plaster added to 2 pounds of water makes 81 cubic inches.

Here is the finished bat. 50 pounds of plaster and 36.6 pounds of water.

I always line the bat with a double layer of cotton sheet and then pour in the slip. After a couple of days the sheet can be removed with the clay and the bat can be allowed to dry. With these new molds that might not be necessary, but I will probably still do it.

Sunday, March 13, 2011

Owen and Nadia's Pieces -- Part 2

Owen and Nadia's Pieces.

This last week I got to fire Owen and Nadia's pieces. Owen's piece is a dog with an invisible fire hydrant, and Nadia's is a Macaroni Penguin, something which I had never heard of, but sure enough, if you Google Image them, they are there in all their glory. Before Nadia glazed her piece the head came off and we glued it back on. In thinking of what might happen in the firing, I decided to make an executive decision and fire the head separately. It was the right decision. I made a little conical clay support and glued the head to it. Some of the macaroni also came off and I made a little clay pedestal and fired them so that they could have shiny glaze like the pieces do. Here they are unfired just before stacking in the kiln.

And here they are fired, but not assembled.

Dupuytren's -- The Surgery

Friday was the day that I went to see Dr Eaton at The Hand Center in Jupiter to get my hand fixed. It turns out that I had something that had to be removed and the surgery that I thought I was going to have was not going to work; there was a skinny tunnel into the hand about the diameter of the metal part of a wooden needle tool and about an inch long and covered with hardened fascia, and it was going to have to be removed. I had driven 300 miles and so Dr Eaton just numbed up the hand and we waited for about an hour for all the components of the medicine to work. There was the anesthetic, of course, and then there was epinephrine which is a vaso-constrictor which helps with bleeding, about 3 cups of coffee worth, taken in about 1 minute. Soon I was just zooming.

Dr Eaton's mom is a potter so he has a real appreciation for potters. All through his childhood there was a wheel and kiln at his house, and his mom made pots.

The reason I went to see him is that my friend Alan Stowell, guitarist, violinist, mandolinist extrordinaire had a Dupuytren's repaired several years ago using needles and all traces of it are totally gone. So I already knew that Dr Eaton was an incredible craftsman, and I felt totally comfortable with him and the staff.

I sat in a chair and watched the whole thing and it was fun in a weird sort of way. Anne and her sister Trish were walking on Jupiter Beach but they came over to the office when they found out that this was going to be more involved than we had originally thought. When they got to the office they said that it sounded like we were having a party back in the operating room -- lots of laughing and carrying on. Friday afternoon, you know.

Here is a photo where Dr Eaton is holding the tunnel just before removal. Don't look if this sort of thing will not be interesting to you.

I can't make pots for a couple of weeks but have talks to prepare for NCECA related events so this is a good time -- and it's over!

Saturday, February 26, 2011


Jim asked about the oilspot bowls and so here is one from today's firing. It was in the bottom of the kiln, and it only went to cone 8, so it's kind of muddy and not as nice as the ones from the last firing, which were hotter. I have plans to open up the bagwall in my kiln so that more heat gets to the bottom, but this firing was all about two very large copper red covered jars, and the kiln was fired to maximize them, so these bowls were an afterthought as it were.

The bowl below was in the previous firing and it's much nicer, at least to me. These two bowls were identical before putting them in the large kiln, in fact the bowl below was the one I deemed to be the worst of the batch. There were 4 bowls in this firing and I will probably fire them again, or at least pick the worst one and fire it.
The large jars are nice, but I want to fire them again because I think I can make them nicer.

Thursday, February 24, 2011

Firing Today in Car Kiln

After struggling with the flu/cold for the last week, I was finally able to fire the large gas kiln today. It was actually the first day that I have had enough energy to do this firing, although the pots have been ready for a week. The photo below is of two large covered jars, which if all goes well, will be a beautiful copper red. So much can go wrong with these and I am a bit apprehensive, though it appears that things went well.

Above this saggar, are several shelves of dinner plates and bowls, and a couple of horse sculptures by my friend Bill Schaaf. There are also some oilspot bowls hiding here and there.

I must say that when I tried to push the car in, things were a little cramped and minor surgery had to be performed to get the car to settle correctly, well not quite correctly, but close. There was about a quarter inch at the bottom where the car did not touch and I did not notice it until the kiln was already hot.